Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$195.45	10.223%	$215.4309	$215.43	$215.45	$215.40
Purchase #2	$109.35	10.477%	$120.8066	$120.81	$120.80	$120.80
Purchase #3	$127.84	7.814%	$137.8294	$137.83	$137.85	$137.80
Purchase #4	$193.89	9.211%	$211.7492	$211.75	$211.75	$211.70
Purchase #5	$50.50	6.263%	$53.6628	$53.66	$53.65	$53.70
Purchase #6	$29.38	13.621%	$33.3818	$33.38	$33.40	$33.40
Purchase #7	$104.97	13.792%	$119.4475	$119.45	$119.45	$119.40
7 purchase totals =	$811.38		$892.3082	$892.31	$892.35	$892.20